a) Field of the Invention
The present invention relates to a method and apparatus for detection of a vacuum leak of a vacuum vessel provided in an equipment such as an absorption chiller and in which a refrigerant and working fluid are charged.
b) Prior-art Statement
In an absorption chiller, for example, water used as refrigerant and a lithium bromide solution used as working fluid are charged in a closed vessel. Generally, the water and solution are kept under a pressure lower than the barometric pressure. More particularly, the delivery port of a solution pump is kept under a negative pressure. The low-pressure side is kept at 0.9 to 2.0 kPa while the high-pressure side is at 2.7 to 5.3 kPa. Therefore, if the airtightness of the closed vessel is poor, the atmosphere will come into the closed vessel.
Conventionally, there was not available any technology which could detect a vacuum leak quickly, easily and with a high sensitivity by a simple apparatus. Namely, it was not until the absorption chiller showed a degradation in refrigerating ability caused by a vacuum leak that the entry of the atmosphere into the closed vessel was found out. To find out early on about such vacuum leak, it is well known to use (a) a soapy water method, (b) halogen gas method and (c) helium pressure detection method. To effect any of such conventional methods, however, the chiller must be put out of operation, charged with such nitrogen gas to pressurize the chiller, and thus they cannot readily be carried out.
The use of soapy water is a classic method for detecting a leak. It is of no practical use since it cannot be done with a high sensitivity and takes much labor and time. Also, to detect such vacuum leak by any one of these methods (a), (b).and (c), the absorption chiller under inspection must be put out of operation and the refrigerant (water) and lithium bromide solution (working fluid) must be discharged from the chiller. These are great disadvantages of the prior art.